For ChIP, cells were sonicated to produce chromatin fragments of 200 base-pairs, lysates were clarified by sedimentation and histone-DNA or lamin-DNA complexes were isolated from supernatants by ChIP using specific antibodies. RNA was purified from cell lysates using the RNEasy mini kit (Qiagen). ChIP sequencing libraries were prepared according to Illumina protocols for sequencing at the Norwegian Sequencing Center.